Aerodynamic characteristics of low Reynolds number airfoils

Abstract

Original scientific paper Assessment of airfoil aerodynamic characteristics is essential part of any optimal airfoil design procedure. This paper illustrates rapid and efficient method for determination of aerodynamic characteristics of an airfoil, which is based on viscous-inviscid interaction. Inviscid flow is solved by conformal mapping, while viscous effects are determined by solving integral boundary layer equations. Displacement thickness is iteratively added to the airfoil contour by alternating inviscid and viscous solutions. With this approach efficient method is developed for airfoil design by shape perturbations. The procedure is implemented in computer code, and calculation results are compared with results of XFOIL calculations and with experiment. Eppler E387 low Reynolds number airfoil and soft stall S8036 airfoil are used for verification of developed procedure for Reynolds numbers 200000, 350000, and 500000. Calculated drag polars are presented in this paper and good agreement with experiment is achieved as long as small separation is maintained. Calculated positions of laminar separation, reattachment, and turbulent separation closely follow experimental measurement. The calculations are performed in relatively short time, which makes this approach suitable for low Reynolds number airfoil design. Keywords: airfoil design; boundary layer features; computational aerodynamics, conformal mapping; laminar separation bubble; low Reynolds number Aerodinamičke karakteristike aeroprofila za niske Rejnoldsove brojeveIzvorni znanstveni članak Procjena aerodinamičkih karakteristika aeroprofila je suštinski dio bilo kakve optimalne konstrukcije aeroprofila. Ovaj rad ilustrira brzu i efikasnu metodu za određivanje aerodinamičkih karakteristika aeroprofila, a utemeljena je na viskozno-neviskoznoj interakciji. Neviskozno strujanje je riješeno konfornim preslikavanjem, dok je doprinos viskoznih efekata određen rješavanjem jednadžbi graničnog sloja u integralnom obliku. Debljina istiskivanja graničnog sloja je iterativno dodavana konturi aeroprofila smjenjivanjem neviskoznog i viskoznog proračuna. Time je ostvaren efikasna metoda za konstruiranje aeroprofila variranjem njegovog oblika. Procedura je primijenjena u obliku računarskog programa, a rezultati proračuna su uspoređeni s rezultatima XFOIL programa i s eksperimentima. Eplerov aeroprofil za niske Rejnoldsove brojeve, E387, i aeroprofil S8036 s blagom stoling karakteristikom su primijenjeni za verifikaciju proračuna za Rejnoldsove brojeve 200000, 350000 i 500000. U radu su prikazane izračunate polare koje se dobro slažu s eksperimentima dokle god su otcjepljenja strujanja mala. Izračunati položaji mjesta laminarnog otcepljenja, pripajanja i turbulentnog otcjepljenja blisko prate eksperimentalne rezultate. Proračun se odvija relativno brzo što mu omogućava primjenu za konstrukciju aeroprofila pomoću variranja njegovog oblika.

Optimization of Low Reynolds number airfoil design using Full Inverse Design method

“…The procedure for the determination of airfoil velocity distribution is paramount in the inverse design method since the designer has the responsibility of specifying the velocity distribution that meets mission requirements. To compute airfoil velocity distribution, the conjugate velocity complex in the z-plane is described as (Abobaker et al, 2017);…”

Design and aerodynamic characteristics analysis of propellers for a novel rescue unmanned aerial vehicle

“…Because the UAV was estimated to be in the low Reynolds number range during flight, the low Reynolds number airfoil is selected as the design airfoil. The commonly used low Reynolds number airfoils include RAF 6, CLARK Y and EPPLER 387 (Ma and Liu, 2009; Lei and He, 2015; Abobaker et al , 2017).…”

Studi Eksperimental Karakteristik Aliran Melalui Silinder Sirkular Dengan Bodi Pengganggu Airfoil NACA 0012, NACA 0018, NACA 0024 Tersusun Tandem

“…Kemudian analisa grafik CP dengan pergeseran titik stagnasi yang terjadi akan membandingkan dengan data pada angle of attack 𝛼 = 0° 𝑑𝑎𝑛 5° [5]. Dapat terlihat pada Gambar 3, titik stagnasi terjadi pada sisi lower side dimana semakin jauh jarak S/D titik stagnasi lebih bergeser ke sudut 0°.…”

“…Pada nilai S/D yang lebih besar, lapisan geser yang termasuk dalam aliran bebas yang melewati airfoil dapat menyentuh silinder. Dapat disimpulkan bahwa pergeseran titik stagnasi dipengaruhi oleh shear layer dan wake yang terlepas dari airfoil yang kemudian mengenai permukaan silinder [5].…”

“…Pada Gambar 10 terlihat bahwa kedua grafik tersebut memiliki kesamaan yaitu pada distribusi CP upper side dan lower side silinder tidak simetris. Hal tersebut dipengaruhi oleh efek dari angle of attack, karena kemiringan airfoil, lapisan geser mengikuti permukaan bawah airfoil melewati bagian bawah silinder dan oleh karena itu terjadi penurunan tekanan pada daerah 𝛼 = 260°− 280° [5].…”